Which two conditions would be a reason to update an existing Data Collector?

According to the Data Collectors document1, a data collector is a configuration that captures application data from a method invocation or an HTTP request. A data collector is associated with a specific method signature or an HTTP parameter name. Therefore, if a new class and method have been deployed to the application, or a new method parameter has been added to an instrumented class, the existing data collector may not match the new code and may need to be updated. However, if the business transaction has been deprecated, or a new HTTP parameter has been added to an existing business transaction, the existing data collector may still work as expected, unless the data collector is specifically configured to filter by the business transaction name or the HTTP parameter value. References:

Data Collectors